The Sun



The way the Sun is made
At the centre of the Sun hydrogen gas is squashed together under such immense pressure that it turns into helium gas. This releases unimaginable amounts of energy.
The energy passes out from the core into the radiation zone then into the convection zone. Finally, the energy escapes from the Sun's surface. There are sunspots and solar flares on the Sun's surface.

Stars

Are all stars like the Sun?
No. Some stars are larger and some are smaller. Stars also vary in colour. The largest stars are blue or white and there are also large and small yellow stars. The Sun is a small yellow star. There are also large and small orange stars and red stars. Some small stars are white.

How can coloured stars be seen?
You can see a few coloured stars if you look carefully into a night sky with the naked eye. You can see more with a pair of binoculars, and even more with a telescope. Never use binoculars or a telescope to look at the Sun. The strong light may blind you.


What is a constellation?
A constellation is a group of stars that people have thought looks like a shape in the sky. The plough, for example, is a common group of stars that people fit together.
The stars in a constellation may not be close together. They just look close to each other as they appear from Earth. In the past, people have seen all kinds of shapes in the stars. Today just over eighty are used. Some show the shape of an ancient god, while others may be animals or even objects such as the microscope and telescope.



Why do people use constellations
The constellations form a sky map. They help astronomers find their way around the sky. As the Earth moves in its orbit different constellations appear in the sky. In the past these helped people to judge the time of the year.

Do other stars have planets?
Some stars have been found to have planets going round them. The planets cannot be seen because the star's light is too bright, but we know the planets are there because they make the star wobble. Stars spin round like planets. The Sun, for example, takes twenty-five days to spin round once. As it spins, the gravity of the planets tug on it and make it wobble very slightly. Astronomers have found other stars that wobble and have been able to work out how many planets are going round the star. They can also calculate the size of the planets and their distances from the stars. In the future, telescopes will be made to see if oxygen and water can be detected on the planets. If oxygen and water do exist, the planets may be home to living things.


How long do stars shine?
It depends on the size. Some really large stars may only last for a few billion years, while smaller ones like the Sun may shine for 10 billion years.

Why does a star stop shining?
It stops because it runs out of hydrogen to turn into helium.

What happens when a star runs out of hydrogen?
If it is a large star, it explodes and forms a supernova. If it is a smaller star, it may swell up and become red. This kind of star is called a red giant. It will then puff away gas and dust and form a small white dwarf star which eventually fades away to form a black dwarf - a dark cinder in space.

What will happen to the Sun?
It will become a red giant in about five billion years time. It will engulf Mercury and Venus and roast the Earth. Then it will turn into a white dwarf and finally a black dwarf. If people still exist at this time they will have moved to another star.